_____scores of times,but he still couldn't understand it.A.Having_英语解答

_____scores of times,but he still couldn't understand it.
A.Having explained
B.Having been explained
C.Though it was explained
D.It was explained
为什么不选B呢?

人气：372 ℃　时间：2019-10-20 00:16:19

解答

D
因为后面用了but,所以前面的句子一定要是一个独立的句子,只有D是一个独立的句子.